# Lifting Remodels Fast-Twitch Fibers Most, and One Protein Grew Muscle in Mice

_Evidence Level: Preliminary · Moesgaard L et al., Nature communications, DOI 10.1038/s41467-026-77275-9_

*Sex- and fiber type-specific remodeling of the muscle proteome implicates CSRP3 in resistance training-induced hypertrophy.*

- **Evidence Level**: Preliminary
- **Why this grade**: Eight-week training study in people with a mouse follow-up, yet the sample size is unstated and the CSRP3 link is shown only in mice.
- **Facts**: Duration: 8 weeks · Funding: Novo Nordisk Foundation
- **Publication Types**: Journal Article, Research Support, Non-U.S. Gov't
- **Journal**: Nature communications
- **Sample Size**: Adult men and women (number not stated), plus mice
- **Authors**: Moesgaard L, Moreno-Justicia R, Schmalbruch J, Jessen S, Stocks B, Andersen NR, Nielsen JJ, Yonamine CY, Treebak JT, Bangsbo J, Prats C, Sylow L, Deshmukh AS, Hostrup M
- **Graded and published**: 2026-09-02
- **Last edited**: 2026-10-05
- **Topics**: Resistance Training, Muscle, Aging
- **DOI**: https://doi.org/10.1038/s41467-026-77275-9
- **Free full text**: https://pmc.ncbi.nlm.nih.gov/articles/PMC13631314/
- **Original Source**: https://pubmed.ncbi.nlm.nih.gov/42823422/

## Summary

Eight weeks of resistance training reshaped the proteins inside fast-twitch muscle fibers far more than in slow-twitch ones, in both men and women. Researchers analyzed muscle from people before and after training, then boosted one standout protein, CSRP3, in mice, which increased their muscle mass. For anyone lifting to stay strong with age, this helps explain why fast-twitch fibers matter so much for growth. The CSRP3 muscle-building effect has only been shown in mice so far.

## Practical Takeaway

This study suggests resistance training strongly reshapes fast-twitch fibers, which seem central to muscle growth.

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